Modular clutch

ABSTRACT

A modular clutch includes a flywheel 2, a clutch cover assembly 3 and a clutch disk assembly 4, which form a single module that in one embodiment is installed directly onto the crankshaft of an engine, and in an alternate embodiment is attached to a flex plate. The modular clutch is configured to be installed and replaced as a unit. The clutch cover assembly 3 has a clutch cover 21, a pressure plate 22 and diaphragm spring 23. The clutch disk assembly 4 has a clutch engagement portion 31 made of a metallic sintered body.

RELATED U.S. APPLICATION DATA

The following application is a division of application Ser. No.08/862,507, filed May, 23, 1997, which is a continuation-in-part of U.S.patent application Ser. No. 08/796,896, filed Feb. 6, 1997, now U.S.Pat. No. 5,730,266, which is a continuation of Ser. No. 08/546,395,filed Oct. 20, 1995, now U.S. Pat. No. 5,645,150, which is acontinuation of Ser. No. 08/331,206, filed Oct. 28, 1994, now abandoned,which is a continuation of Ser. No. 08/035,116, filed Mar. 19, 1993, nowissued as U.S. Pat. No. 5,392,888.

BACKGROUND OF THE INVENTION

A. Field of the Invention

The present invention relates to a modular clutch mechanism, and inparticular to a modular clutch mechanism in which a flywheel, a clutchcover assembly and a clutch disk assembly form a single module that isinstalled and replaced as a single unit on a crankshaft of an engine.

B. Description of the Background Art

A clutch device generally includes a flywheel fixed to a crank shaft ofan engine, a clutch cover assembly fixed to the flywheel and a clutchdisk assembly arranged between the flywheel and the clutch coverassembly. Typically, the flywheel, clutch disk assembly and the clutchcover assembly are separate elements, each being repairable andreplaceable irrespective of the other elements.

In prior art clutch devices, the flywheel is bolted to the crankshaft ofthe engine. The clutch cover assembly is bolted to the flywheel and theclutch disk assembly is sandwiched between the flywheel and the clutchcover assembly. Replacement of any one element may be achieved byremoving the bolts on the clutch cover assembly, removing the clutchcover assembly and the clutch disk assembly and replacing either asnecessary. The flywheel may then also be serviced or replaced asnecessary.

A problem with the above prior art configuration is that the components,the flywheel, clutch cover and clutch disk assemblies are generallyexpensive to manufacture and are sometimes costly to service. Typically,both the clutch cover and clutch disk assemblies are replaced togethereven if only one of the two components is worn or damaged. As well, theflywheel is typically resurfaced upon replacement of the clutch disk andclutch cover assemblies. Therefore, all three components are renewedeven if only one of the components is worn or damaged.

Recently, modular clutches have been introduced where the flywheel,clutch cover assembly and clutch disk assembly are assembled in advanceto form a single module. Such a modular clutch is fixed to the crankshaft of the engine as a single unit. For example, a flexible plate isfixed in advance to the end of the crankshaft of the engine. An outerperipheral portion of the flexible plate is bolted to an outerperipheral portion of the flywheel. In this case, bolts are insertedfrom the engine side.

In the conventional modular clutch described above, the clutch cover andthe flywheel are fixed together by welding, or the like without usingbolts. Elimination of bolts allows reduction in weight and cost. In thissemi-permanently fixing manner using caulking, welding or the like, themodular clutch must be entirely exchanged when a friction facing of theclutch disk assembly is worn to the limit. In the prior art modularclutch it is possible that the clutch disk assembly may become worn toits limit while the flywheel and clutch cover assembly are still usable.It is not possible to replace the clutch disk assembly easily using themodular construction described above. Therefore it is desirable toinsure that the clutch disk assembly has as long a usable life aspossible.

SUMMARY OF THE INVENTION

An object of the invention is to provide a modular clutch in which aclutch cover and a flywheel can be fixed together by a simple structurewithout any disadvantage.

Another object of the present invention is to prolong the life of amodular clutch.

In accordance with one aspect of the present invention, a modular clutchis configured as a single module for connection the output of an engineand includes a flywheel formed with a friction surface on one side andconfigured to be removably attached a torque output member of an engine.A clutch cover assembly includes a clutch cover that is fixed to theflywheel, a pressure plate being disposed inside the clutch cover, thepressure plate having a pressing surface facing the friction surface.The clutch cover assembly further includes a biasing member supported inthe clutch cover for biasing the pressure plate against the flywheel. Aclutch disk assembly is disposed between the friction surface and thepressing surface, the clutch disk assembly having a plurality offriction facings disposed between the friction surface and the pressingsurface, the friction facing being formed of a metallic frictionmaterial.

Preferably, the clutch cover is caulked to the flywheel.

Preferably, the clutch cover is welded to the flywheel.

Preferably, the clutch cover is riveted to the flywheel.

Preferably, the modular clutch further includes a ring gear disposedabout the clutch cover and the clutch cover encompasses an outerperiphery of the flywheel, the ring gear being shrink-fitted about theclutch cover such that the ring gear causes the clutch cover to firmlyengage the outer periphery of the flywheel.

Preferably, the flywheel includes a first flywheel and an inertiamember, and a torsional vibration damper mechanism is disposed betweenthe first flywheel and the inertia member, the torsional vibrationdamper mechanism allowing limited relative rotation between the firstflywheel and the inertia member and further damping vibrationtherebetween.

Preferably, the torsional vibration damper mechanism is formed with achamber having an elastic member disposed therein, and a powder solidlubricant is further disposed within the chamber.

Preferably, the elastic member is a bent, undulated plate spring.

Preferably, an outer peripheral portion of the bent plate springcontacts an peripheral wall of the accommodating chamber therebydefining a friction generating mechanism which generates frictiontherebetween in response to relative rotation between the first flywheeland the inertia member.

Preferably, the powder solid lubricant is made of molybdenum disulfide.

Preferably, the powder solid lubricant is made of tungsten disulfide.

Preferably, the clutch disk assembly further includes a cushioningmember capable of elastically deformation in an axial direction, and thefriction facings are fixed to opposite surfaces of the cushioningmember, respectively.

Preferably, the first flywheel and the pressure plate are made of castiron containing Cr, V and a rare earth element added thereto.

In accordance with another aspect of the present invention, a modularclutch construction includes a flywheel having an end face configuredfor connection to a crankshaft of an engine, the end face also having acircumferentially peripheral bulge protruding axially, the axialprotrusion increases along a direction of increasing flywheel radius. Aclutch cover assembly includes a clutch cover encompassing the flywheeland axially positioning relative to the flywheel, the clutch coverhaving a bent rim inwardly bent so as to clamp the peripheral bulgebeing provided with retaining elements fixed to the input end face, theclutch cover being dish-shaped and having a peripheral wall axiallyextending over the clutch disc assembly, the input end face having aplurality of circumferentially spaced pedestal portions corresponding tothe retaining elements, the retaining elements being formed along thebent rim, each of the retaining elements being bent radially inwardflush with a surface of the pedestal portions, the clutch cover assemblyfurther including a pressure plate coaxial with the flywheel and facingan opposite end face of the flywheel. A clutch disk assembly iscoaxially disposed with respect to the pressure plate and the flywheeland is disposed therebetween, Friction portions of the clutch diskassembly are formed of a sintered metal material. Fasteners fix theclutch cover retaining elements to the pedestal portions. A portion ofthe clutch cover peripheral wall is stepped radially inward, forming anabutment which abuts marginally against the opposite end face of theflywheel.

Preferably, the flywheel and the pressure plate are made of cast ironcontaining Cr, V and a rare earth element added thereto.

In accordance with yet another aspect of the present invention, amodular clutch construction includes a flywheel having an annularportion formed with an outer radial surface, a first axial face isconnectable to a corresponding member of an engine for power input tothe clutch, the first axial face having a peripheral bulge extendingaxially, and a second axial face opposite the first axial face. A clutchcover assembly has:

(a) an annular pressure plate having an outer radial surface, coaxiallydisposed adjacent to the flywheel and facing the second axial face;

(b) an urging member attached to the pressure plate for elasticallyurging the pressure plate toward the flywheel;

(c) a unitary clutch cover including an annular wall encompassing theouter radial surfaces of the pressure plate and the flywheel, a caulkingportion extending from the annular wall to be caulked to the peripheralbulge, a fixation portion extending from the annular wall to be fixed tothe second axial face, and a support portion for supporting the urgingmember.

A clutch disc assembly coaxially is disposed between the pressure plateand the flywheel, friction portions of the clutch disk assembly beingformed of a sintered metal material;

Preferably, the flywheel and the annular pressure plate are made of castiron containing Cr, V and a rare earth element added thereto.

Preferably, the peripheral bulge has an arcuate shape, and the caulkingportion has an arcuate shape corresponding to the peripheral bulge.

Preferably, the peripheral bulge extends outwardly in an axial directionadjacent to a peripheral edge of the

Preferably, the annular wall has a second caulking portion caulked to aperipheral edge of the second axial face of the flywheel, the flywheelbeing axially sandwiched b

Preferably, the second caulking portion of the clutch cover is steppedradially inward and abuts against the second

Preferably, the annular wall has a second caulking portion caulked to aperipheral edge of the second axial face of the flywheel, the flywheelbeing axially sandwiched between the caulking portion and the secondcaulking portion.

Preferably, the second caulking portion of the clutch cover is steppedradially inward and abuts against the second

Preferably, the peripheral bulge extends outwardly in an axial directionadjacent to an outer radial edge of the flywheel.

Preferably, the annular wall has a second caulking portion caulked to aperipheral edge of the second axial face of the flywheel, the flywheelbeing axially sandwiched between the caulking portion and the secondcaulking portion.

Preferably, the second caulking portion of the clutch cover is steppedradially inward and abuts against the second axial face of the flywheel.

Preferably, the annular wall has a second caulking portion caulked to aperipheral edge of the second axial face of the flywheel, the flywheelbeing axially sandwiched between the caulking portion and the secondcaulking portion.

Preferably, the second caulking portion of the clutch cover is steppedradially inward and abuts against the second end face of the flywheel.

In still another aspect of the present invention, a modular clutchconstruction includes a flywheel having an outer radial surface and anaxial face and an annular pressure plate having an outer radial face,the annular pressure plate being coaxially disposed adjacent to theflywheel and facing the axial face of the flywheel. A clutch coverencompasses the outer radial surfaces of the pressure plate and theflywheel, a radial inner surface of the clutch cover contacting theouter radial surface of the flywheel at a contact position. A ring gearis fitted onto a peripheral surface of the clutch cover radially overthe contact position, the ring gear being shrunk fitted on theperipheral surface of the clutch cover. A plurality of axially extendingslits are formed circumferentially spaced on an interior margin of theclutch cover at the contact position. A clutch disc assembly coaxiallydisposed between the pressure plate and the flywheel, friction portionsof the clutch disk assembly being formed of a sintered metal material.

Preferably, a positioning means maintains a fixed relative positionbetween the clutch cover and the flywheel.

Preferably, the positioning means includes a plurality of holes formedin the clutch cover and the flywheel having pins inserted therein, theholes being spaced respectively about the circumference of the clutchcover and the flywheel in alignment with the contact position.

Preferably, the positioning means includes an abutment portion formed asa radially inward step on the clutch cover, the abutment portionabutting the axial face of the flywheel at a radially outward position.

Preferably, the modular clutch construction further includes a flexibleplate mountable to a second axial face of the flywheel.

Preferably, the flywheel and the annular pressure plate are made of castiron containing Cr, V and a rare earth element added thereto.

The foregoing and other objects, features, aspects and advantages of thepresent invention will become more apparent from the following detaileddescription, when taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic cross section view of a modular clutch inaccordance with a first embodiment of the present invention, where themodular clutch is attached to a flexible plate mounted on a crankshaftof an engine;

FIG. 2 is a fragmentary plan of a cover coupling portion of the modularclutch depicted in FIG. 1, with the modular clutch removed from theflexible plate;

FIG. 3 is a fragmentary cross section view of a portion of the modularclutch depicted in FIG. 1, on an enlarged scale, showing further detailsof the cover coupling portion depicted in FIG. 2;

FIG. 4 is a fragmentary plan of a disk plate of a clutch disk assemblyof the modular clutch depicted in FIG. 1, with the clutch disk assemblyshown removed from the modular clutch;

FIG. 5 is a schematic cross section of a portion of the clutch diskassembly depicted in FIG. 4, showing details of a friction pad of theclutch disk assembly in accordance with the first embodiment of thepresent invention;

FIG. 6 is a fragmentary plan of a clutch disk assembly in accordancewith a second embodiment of the present invention;

FIG. 7 is a schematic cross section of a portion of the clutch diskassembly depicted in FIG. 6, taken along line VII--VII in FIG. 6,showing details of a friction pad and cushioning plate of the clutchdisk assembly in accordance with a second embodiment of the presentinvention;

FIG. 8 is a cross section taken along line VIII--VIII in FIG. 6;

FIG. 9 is a schematic cross section view of a modular clutch inaccordance with a third embodiment of the present invention, having analternate means of attaching a clutch cover assembly to a flywheel;

FIG. 10 is a fragmentary cross section view of a portion of the modularclutch depicted in FIG. 9, on an enlarged scale, showing details of themeans for attaching the clutch cover assembly to the flywheel;

FIG. 11 is a fragmentary elevation of a portion of the exterior ofclutch cover assembly of the modular clutch depicted in FIG. 9;

FIG. 12 is a fragmentary cross section view similar to FIG. 10, of amodified portion of the modular clutch depicted in FIG. 9, on anenlarged scale, showing slightly modified details of the means forattaching the clutch cover assembly to the flywheel;

FIG. 13 is a schematic cross section view of a modular clutch inaccordance with a fourth embodiment of the present invention, having afurther means of attaching a clutch cover assembly to a flywheel;

FIG. 14 is a schematic cross section view of a modular clutch inaccordance with a fifth embodiment of the present invention,, havingfurther means of attaching a clutch cover assembly to a flywheel;

FIG. 15 is a schematic cross section view of a modular clutch inaccordance with a sixth embodiment of the present invention, having acover coupling unit as a means of attaching a clutch cover assembly to aflywheel;

FIG. 16 is a fragmentary perspective view of the cover coupling unit ofthe modular clutch depicted in FIG. 15,, on a slightly enlarged scale;

FIG. 17 is a schematic cross section view of a modular clutch inaccordance with a seventh embodiment of the present invention, havingflywheel directly attached to the crankshaft of the engine;

FIG. 18 is a fragmentary plan of a diaphragm spring shown removed fromthe modular clutch depicted in FIG. 17;

FIG. 19 is a fragmentary perspective view of an aperture formed in thediaphragm spring depicted in FIG. 18;

FIG. 20 is a fragmentary perspective view of an alternately formedaperture in the diaphragm spring depicted in FIG. 18;

FIG. 21 is a part elevation, part cut away and part plan view of amodular clutch in accordance with an eighth embodiment of the presentinvention;

FIG. 22 is a side schematic cross section view of the modular clutchdepicted in FIG. 21, taken along the line XXII--XXII in FIG. 21;

FIG. 23 is a fragmentary, cross sectional view similar to FIG. 22, takenalong the line XXIII--XXIII in FIG. 21;

FIG. 24 shows lubrication characteristics of various kinds of solidlubricants employable in the eighth and ninth embodiments of the presentinvention; and

FIG. 25 is a cross section view of a modular clutch in accordance with aninth embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

First Embodiment

A modular clutch 1 shown in FIG. 1 includes a flywheel 2, a clutch coverassembly 3 and a clutch disk assembly 4 which form a single modularassembly. An engine E is disposed at the left side of FIG. 1, and atransmission T is disposed at the right side of the figure. In FIG. 1,O--O represents a rotation axis of the modular clutch 1. Hereinafter,toward the left side of FIG. 1 will be referred to as the engine sideand toward the right side of FIG. 1 will be referred to as thetransmission side.

The modular clutch 1 is a device for transmitting and interrupting atorque from a crank shaft 5 of the engine to a main drive shaft 6extending from the transmission. The modular clutch 1 is configured tobe installed and removed from the engine E as a single unit. The modularclutch 1 is attached to a flexible plate 7 which is fixed to the end ofthe crank shaft 5 by a plurality of bolts 12. The flexible plate 7 has ahigh rigidity in the rotating direction but is flexible in the bendingdirection (axial directions). A ring gear 13 is fixed to the outerperipheral portion of the flexible plate 7, for instance, by welding. Aflywheel 2, described below, of the modular clutch 1 is fixed to theouter peripheral portion of the flexible plate 7 by a plurality of bolts11. The main drive shaft 6 has spline gear teeth that spline engage ahub 34 of the clutch disk assembly 4 and is described below. A releasedevice 8 is axially movably arranged around the main drive shaft 6. Therelease device 8 can engage with a transmission side of a diaphragmspring 23, described below, of the clutch cover assembly 3.

The flywheel 2 has a substantially annular shape, and has a flatfriction surface 2a faced toward the transmission. The flywheel 2 ismade of, for instance, cast iron containing Cr, V and a rare earthelement.

As shown in FIGS. 2 and 3, the flywheel 2 is provided with a pluralityof inclined grooves 2c extending in the circumferential direction on anouter peripheral side surface thereof, facing the engine side. Eachinclined groove 2c has an inclined bottom which increases the depth asthe position moves from the radially outer side toward the inner side ofthe flywheel 2. Flat portions 2d are formed between adjacent inclinedgrooves 2c. Each flat portion 2d has a hole H of a predetermined depthat its substantially center portion.

The clutch cover assembly 3 includes a clutch cover 21, a pressure plate22 and a diaphragm spring 23. The clutch cover 21 has a dish-like plateshape. The clutch cover 21 has a large aperture at its center throughwhich the shaft 6 extends. The outer peripheral wall of the clutch cover21 extends axially, and has an end fixed to the outer peripheral portionof the flywheel 2.

Description will now be given on a cover fixing unit 61 which serves tofix the flywheel 2 and the clutch cover 21 to one another. The clutchcover 21 is provided at its axial end with an outer cover portion 62,which wraps about portions of the outer peripheral surface 2b of theflywheel 2 and is in direct contact therewith. The end of the outercover portion 62 is provided at its end with a plurality of caulkingportion 63 which correspond in circumferential length to the inclinedgroove 2c. The outer cover portion 62 is also provided with a fixingportion 64 sized and shaped to generally correspond to the flat portion2d, as is shown in FIG. 2. The caulking portion 63 is bent to conformand cover the inclined groove 2c on the flywheel 2, as shown in FIG. 3.The fixing portion 64 extends radially inward beyond the caulkingportion 63, and is in close contact with the flat portion 2d of theflywheel 2. The fixing portion 64 is fixed to the flat portion 2d by apin 68 which is inserted into the hole H. In this manner, relativerotation between the flywheel 2 and the clutch cover 21 is prevented.Further, the clutch cover 21 is provided at an outer peripheral portionwith an annular contact portion 65 which is caulked to extend radiallyinwardly, and is in contact with the outer peripheral edge of thefriction surface 2a of the flywheel 2 from the transmission side, as isshown in FIG. 3. The contact portion 65 has a recessed surface which isin contact with an outer radial portion of the friction surface 2a. Whenthe clutch cover 21 is fitted to the outer periphery of the flywheel 2,this recessed surface is in contact with the friction surface 2a of theflywheel 2 so that the flywheel 2 is axially positioned with respect tothe clutch cover 21.

The pressure plate 22 is an annular member disposed radially inside theclutch cover 21. The pressure plate 22 is made of, for instance, castiron containing Cr, V and a rare earth element. The pressure plate 22has a pressing surface 22a facing toward the flywheel 2. The pressureplate 22 has an annular projection 22b which projects in an axialdirection from the surface opposite to the pressing surface 22a. Ends ofa plurality of strap plates 24 which extend tangentially are fixed tothe outer peripheral portion of the pressure plate 22 by bolts 28, asshown in FIG. 1. The other end of each strap plate 24 is fixed to theclutch cover 21. The strap plates 24 cause the pressure plate 22 canrotate together with the clutch cover 21 but allow for axial movement ofthe pressure plate 22 with respect to the clutch cover 21. These strapplates 24 bias the pressure plate 22 away from the flywheel 2.

The diaphragm spring 23 is disposed between the pressure plate 22 andthe clutch cover 21. The diaphragm spring 23 has an annular elasticportion 23a and a plurality of levers 23b extending radially inward fromthe elastic portion 23a. The elastic portion 23a has an outer peripheralportion which is in contact with the annular projection 22b of thepressure plate 22, and has an inner peripheral portion which issupported by a supporting structure 25. The supporting structure 25includes of a plurality of stud pins 26 and two wire rings 27. Theplurality of stud pins 26 each have an end fixed to the radially innerportion of the bottom of the clutch cover 21, and extend toward theengine. These plurality of stud pins 26 support the two wire rings 27. Aradially inner portion of the elastic member 23a is disposed between thetwo wire rings 27. Each stud pin 26 extends through a roundedrectangular aperture 23c at the diaphragm spring 23. The elastic portion23a in this state biases the pressure plate 22 toward the flywheel 2.

The release device 8 is arranged between the diaphragm spring 23 and thetransmission T, and is opposed to the radially inner ends of the levers23b of the diaphragm spring 23. When the release device 8 is movedtoward the flywheel 2, the release device 8 pushes the levers 23 towardthe engine, counteracting the force of the elastic portion 23a acting onthe pressure plate 22 and the pressure plate 22 is no longer urgedtoward the flywheel 2.

The clutch disk assembly 4 includes a clutch engagement portion 31arranged between the flywheel 2 and the pressure plate 22. The clutchdisk assembly 4 also includes clutch and retaining plates 32 and 33which define input members, a hub 34 which defines an output member,coil springs 36 arranged between the plate pair 32 and 33 and a flange35 of the hub 34, and a friction generating mechanism 37. The hub 34 hasa boss 34a which is integrally provided at its outer periphery with theflange 35. The boss 34a is provided at its center with a spline apertureengagable with the main drive shaft 6. The clutch and retaining plates32 and 33 are circular plates arranged at opposite sides of the flange35, respectively. The clutch and retaining plates 32 and 33 haveradially outer portions which are fixed together by contact pins 38. Thecoil springs 36 are arranged in windows formed at the plates 32 and 33and the flange 35. The friction generating mechanism 37 includes aplurality of washers arranged between the plates 32 and 33 and theflange 35.

As shown in FIGS. 3, 4 and 5, the clutch engagement portion 31 isbasically formed of a disk plate 41 fixed to the clutch plate 32 and aplurality of friction pads 43 fixed to the disk plate 41. The disk plate43 is a circular member as shown in FIG. 4, and has an inner peripheralportion fixed to the outer peripheral portion of the clutch plate 32 byrivets 39. The disk plate 41 is provided at its outer periphery withthree projections 42. Each projection 42 supports two friction pads 43on each side (i.e., four pads 43 in total). As shown specifically inFIG. 3, each friction pad 43 is formed of a core plate 45, a screen 46and a sintered body 47. As shown in FIG. 3, each projection 42 and thecore plates 45 of the friction pads 43 at its opposite sides are fixedtogether by two rivets 44. The sintered body 47 is provided withapertures corresponding to the rivets 44.

Referring to FIG. 5 showing, on an enlarged scale, the structure,description will be given on a specific structure of the friction pad43. The screen 46 is disposed on the core plate 45. The screen 46 isformed of a metal mesh plate, and has a corrugated form. The core plate45 and the sintered body 47 are adhered to the tops and bottoms of thescreen 46, respectively. A space between the core plate 45 and thesintered body 47 is filled with particles of graphite 26. The core plate45 is provided at its periphery with a projection 45a for preventingescape of the graphite 26.

The sintered body 47 is arranged on the screen 46, and is made ofmixture of ceramic or graphite powder and powder of Cu-Sn alloy.

In the friction pad 43 thus constructed, the graphite 48 functions as acushioning material between the core plate 45 and the sintered body 47.Thereby, noises during the clutch engaging operation can be reduced. Thegraphite 48 also functions as a heat insulator. As a result, heattransmission from the sintered body 47 to the disk plate 41, clutchplate 32 and retaining plate 33 is minimized, and bowing and deformationof these plate members are suppressed. This results in increase inlifetime of the clutch disk assembly 4.

Since the screen 46 has a corrugated form, it provides cushioningeffect. Since the screen 46 has a mesh form, the graphite 48 can freelymove between its opposite sides. This increases the cushioning effectsof the graphite 48.

A method of manufacturing the friction pad 43 is as follows. First, thescreen 46 is disposed on the core plate 45, and the graphite 48 isarranged substantially entirely over the screen 46. Then, the mixture ofthe powder of ceramics, graphite or the like and the powder of Cu-Sn isdisposed over the graphite 48. These are heated at about 700° C., andare subjected to a predetermined pressure which does not flatten thescreen 46.

A method of assembling the modular clutch 1 is described below. First,the diaphragm spring 23 and the pressure plate 22 are fixed to theclutch cover 21 to assemble them into the clutch cover assembly 21. Atthis time, the caulking portion 63 and the fixing portion 64 of theclutch cover 21 have straight forms. Then, the clutch cover assembly 3and the clutch disk assembly 4 are assembled together, and the flywheel2 is put into the clutch cover 21. In this step, the end surface of theouter peripheral portion of the flywheel 2 is brought into contact withthe contact portion 65 of the clutch cover 21, so that the flywheel 2and the clutch cover 21 are axially positioned together. Then, theapertures at the clutch cover 21 and the flywheel 2 are aligned togetherfor inserting the pin 68 into them.

Thereafter, a caulking step is performed. Thereby, each caulking portion63 of the clutch cover 21 is deformed to conform closely the surface andinclination of the inclined groove 2c of the flywheel 2. Each fixingportion 64 is bent 90 degrees and is pressed against the flat portion 2dof the flywheel 2. Then, the pin 68 is fitted into the apertures at theflat portion 2d of the flywheel 2 and the fixing portions 64. Thisprevents relative rotation between the flywheel 2 and the clutch cover21. After assembling, the modular clutch 1 can be handled as one singlemodule or component.

The completed modular clutch 1 is fixed by the bolts 11 to the flexibleplate 7 which is already fixed to the crank shaft 5. The housing of thetransmission T is provided with windows or holes (not shown) formanipulating the bolts 11.

The structure of the fixing unit 61 in this embodiment does not requirea fastening member such as a bolt, thereby reducing the weight of thepresent invention, as compared to the prior art. Since the flywheel 2and the clutch cover 21 are axially positioned with respect to oneanother by the caulking portion 65, a member such as a knock pin is notrequired, so that the structure is simplified, compared to the priorart, and may also be inexpensive compared to the prior art. Since theouter peripheral end of the clutch cover 21 is fixed to the flywheel 2by caulking, the clutch cover 21 can be reliably fixed to the flywheel 2in a simple manner.

Since this modular clutch 1 uses the friction pads 43 formed of themetallic sintered bodies 47, the clutch engagement portion 31 can have alonger lifetime than that in the prior art. Thus, the modular clutch 1does not require replacement of the clutch disk assembly 4 as often asin prior art configurations without such sintered bodies. Therefore,there is little disadvantage to the modular construction of the presentinvention even though the flywheel 2 and the clutch cover 21 are coupledtogether by caulking.

The first flywheel 2 and the pressure plate 22 are made of cast ironadditionally containing Cr, V and a rare earth element. As a result,wear of the first flywheel 2 and the pressure plate 22 is reduced, andthe whole modular clutch 1 has an increased life expectancy.

Second Embodiment

The clutch engagement portion 31' shown in FIGS. 6 to 8 may be usedinstead of the clutch engagement portion 31' in the first embodiment.The clutch engagement portion 31' is formed with a plurality of clutchcoupling members 51. The plurality of clutch coupling members 51 arefixed to the outer peripheral edge of a disk plate 41, by rivets 60 andare circumferentially equally spaced apart from each other.

Each clutch coupling member 51 is formed of first and second core plates52 and 53 made of steel plates, a cushioning plate 54, and first andsecond sintered bodies 56 and 57 made of a composite material ofceramics and metal, as shown in FIGS. 7 and 8. The first core plate 52and the cushioning plate 54 extend radially inwardly beyond the secondcore plate 53, and the first core plate 52 and cushioning plate 54 arefixed to the disk plate 41 by the rivets 60. A cushioning portion of thecushioning plate 54 has a stepped or corrugated form and is arrangedbetween the first and second core plates 52 and 53. Thus, the cushioningplate 54 has inner and outer peripheries in contact with the first coreplate 52, and a radially middle portion in contact with the second coreplate 53, as is shown in FIG. 8. As is also shown in FIGS. 6 and 8,circumferentially opposite ends of each of the cushioning plates 54 andeach of the second sintered body 57 are fixed together by rivets 55. Thefirst core plate 52 is provided with apertures 52a located at positionscorresponding to the rivets 55. The first sintered body 56 extendscircumferentially between the apertures 52a of the first core plate 52,and the second sintered body 57 is extends circumferentially between therivets 55 of the second core plate 53. The first and second sinteredbodies 56 and 57 are adhered to first and second core plates 52 and 53,respectively.

The cushioning plate 54 can reduce vibration and noises during start ofthe vehicle. The elasticity of the cushioning plate 54 acts in thedirection opposite to the pressing pressure of the pressure plate 22,and therefore reduces a force required for depressing a clutch pedal. Inparticular, since wear of the friction member 57 is suppressed, therelationship between the pressing force required to disengage the clutchand the elastic force of the diaphragm spring does not substantiallyvary over the useable life of the clutch module. Thus, a low pedaldepressing force is maintained. Consequently, it is not necessary toemploy a complicated friction adjusting mechanism.

Alternatively, rubber or other elastic material may be used instead ofthe cushioning plate 54. Alternatively, unwoven fabric such as steelwool having a heat resistance may be employed.

Third Embodiment

A modular clutch 100 shown in FIGS. 9 to 12 has many features that aresimilar to those described above with other embodiments. Therefore,generally, only those features that differ from the modular clutch ofthe first embodiment will be described. In the modular clutch 100, thecover fixing unit 161 has many different features, as described below.The clutch engagement portion 31 is generally the same as that in thefirst embodiment but could alternatively be as described with respect tothe second embodiment.

In the modular clutch 100, a clutch cover 121 is provided at its outerperipheral end with a plurality of outer cover strips 72 which extendaxially. The outer cover strips 72 are defined by a plurality of slits73 which extend axially therebetween, as shown in FIG. 11. The outercover strips 72 cover and contact the outer peripheral surface 2b of theflywheel 2.

A ring gear 13 is shrink-fitted around the outer cover strips 72 of theclutch cover 121. The ring gear 13 is provided at its radially outerportion with gear teeth that mesh with a pinion gear of a starter motor.Apertures 74e and 2e are formed at the outer cover strip 72 of theclutch cover 121 and the outer peripheral surface 2a of the flywheel 2,respectively. A pin 75 is fitted into the apertures 74 and 2e. The pin75 stops relative rotation between the clutch cover 121 and the flywheel2.

The outer cover strip 72 of the clutch cover 121 is tightly fixed to theouter peripheral surface 2b of the flywheel 2 by the shrink-fitted ringgear 13.

An assembling operation of the modular clutch 100 will be describedbelow. First, the clutch disk assembly 4 is arranged inside the clutchcover assembly 3, and the flywheel 2 is inserted into the clutch cover121 of the clutch cover assembly 3. In this operation, the apertures 74and 2e of the clutch cover 121 and the flywheel 2 are aligned together,and the pin 75 is fitted into these apertures. Thereby, the clutch cover121 is prevented from relative rotation with respect to the flywheel 2.

In this state, the ring gear 13 is heated. If necessary, the clutchcover 121 and the flywheel 2 are cooled. Then, the ring gear 13 havingan expanded inner diameter owing to the heating is shrink-fitted to theplurality of outer cover strips 72. The inner diameter of the ring gear13 thus fitted shrinks, so that the outer cover strips 72 of the clutchcover 121 and ring gear 13 are tightly fixed to the outer peripheralsurface 2b of the flywheel 2. Even if the inner diameter of the clutchcover 121 is larger than the outer diameter of the flywheel 2 due to awork error, the plurality of outer cover strips 72 bend inward inaccordance with shrinkage of the ring gear 13, and therefore is broughtinto tight and close contact with the outer peripheral surface 2b. Thus,the clutch cover 121 is reliable fixed to the outer peripheral surface2b owing to provision of the plurality of outer cover strips 72 definedby the plurality of slits 73. In this manner, the modular clutch 100 iscompleted.

In this embodiment, the ring gear 13 is shrink-fitted to the flywheel 2,and simultaneously the clutch cover 121 is fixed to the outer peripheralsurface 2b of the flywheel 2. Therefore, only one step is requiredinstead of conventional two steps, i.e., a step for fixing the ring gearto the flywheel and a subsequent step for fixing the clutch cover to theflywheel. Since the clutch cover 121 and the flywheel 2 are fittedtogether substantially entirely through the outer peripheral surfacesthereof, strong fitting can be maintained for a long term compared witha conventional structure using a plurality of bolts for fixing them.Since a fastening member such as a bolt is not required, the wholestructure can be inexpensive and can have a reduced weight.

In a modification of this embodiment, as shown in FIG. 12, a contactportion 77 may be formed by caulking the outer peripheral portion (nearthe base ends of the outer cover strips 72) of the clutch cover 121radially inward. This contact portion 77 is provided with a contactsurface which is in contact with the outer peripheral edge of theflywheel 2 near the friction surface 2a. The contact between the contactportion 77 and the outer peripheral edge of the flywheel 2 acts toposition axially the clutch cover 121 and the flywheel 2 when fittedtogether. In this case, the pin 75 is not required.

Fourth Embodiment

In a modular clutch 200 shown in FIG. 13, the clutch cover 221 is fixedto the flywheel 2 by rivets. More specifically, a cover fixing unit 261has the following structure. The flywheel 2 is provided at its outerperipheral portion with outer projections 2f which project radiallyoutward. The clutch cover 221 is provided with outer fixing portions 79corresponding to the outer projections 2f, respectively. The outerprojection 2f and the outer fixing portion 79 are fixed together by arivet 81.

Fifth Embodiment

According to a modular clutch 300 shown in FIG. 14, the clutch cover 321is welded to the flywheel 2. More specifically, a cover fixing unit 361has the following structure. The clutch cover 321 has an outerperipheral end which is in contact with the outer peripheral portion 2bof the flywheel 2. The outer peripheral end of the clutch cover 321 isfixed to the outer peripheral surface 2b through a welded portion 82.

Six Embodiment

According to a modular clutch 400 shown in FIGS. 15 and 16, a clutchcover 421 is fixed to the flywheel 2 by bolts. More specifically, acover fixing unit 461 has the following structure. The clutch cover 421is provided at its outer peripheral end with projections 83 projectingaxially from the end surface 421a. The projections 83 are formed over anentire circumference with equal spaces therebetween, and each have anaperture 84 at its center. The flywheel 2 is provided at its outerperipheral surface 2b with grooves 2g. A thread hole 2h which extendsradially is formed within the groove 2g. The groove 2g forms atangential flat seat surface. The projection 84 is engaged with thegroove 2g, and is fixed to the flywheel 2 by a bolt 86.

A manner of assembling the modular clutch 400 will be described below.First, the clutch disk assembly 4 is positioned inside the clutch coverassembly 3, and the flywheel 2 is inserted into the clutch cover 421. Inthis operation, the projection 83 is fitted into the groove 2g of theflywheel 2, and the end surface 421a is brought into contact with of theflywheel 2 near the friction surface 2a, all being axially positionedtogether. In this state, the bolt 86 is inserted into the aperture 84 ofthe fixing portion 83, and is screwed into the thread hole 2h. Thereby,the clutch cover 421 is fixed to the flywheel 2. Since the groove 2gprovides a flat seat surface, the projection 83 of the clutch cover 421is pressed against the groove 2g and thereby is flattened. Thereby,contact between the projection 83 and the surfaces of the groove 2g aswell as a contact area between the projection 83 and the seat surface ofthe bolt 86 provide rigid connection between the clutch cover 421 andthe flywheel 2.

In this embodiment, there is sufficiently large contact between theprojection 83 of the clutch cover 421 and the flywheel 2 and theprojection 83 is fixed by the bolt 86 after the projection 83 is fittedto the groove 2g of the flywheel 2. Therefore, shear forces generated inthe clutch cover 421 do not directly act on the bolt 86. Therefore,there is little possibility of breakage of the bolt. Therefore, it ispossible to minimize the number the bolts required for fixing the clutchcover 421.

Seventh Embodiment

A modular clutch 500 shown in FIGS. 17 to 20 is basically formed of theflywheel 2, the clutch cover assembly 3 and the clutch disk assembly 4.The modular clutch 500 is fixed to the crank shaft 5 in a manner whichis described below.

The friction surface 2a is formed at the transmission side of the outerperipheral portion of the flywheel 2. The flywheel 2 is fixed to thecrank shaft 5 by a plurality of bolts 11A. More specifically, the crankshaft 5 is provided with thread apertures 5a, and the flywheel 2 isprovided with apertures 2i for the bolt 11A.

The clutch cover assembly 3 is basically formed of a clutch cover 521,the pressure plate 22 and the diaphragm spring 23. The clutch cover 521has a dish-like shape, and has a large aperture at its center. Theclutch cover 521 has an outer peripheral portion which extends axiallyand is in close contact with the outer peripheral surface 2b of theflywheel 2, and also has an outer peripheral end which is bent radiallyinward and is engaged with the bottom surface of the flywheel 2 at theengine side. The outer peripheral portion of the clutch cover 521 andthe outer peripheral portion 2b of the flywheel 2 are coupled togetherby a pin 93.

A diaphragm spring 523 is disposed in the cover 521 and is a generallycircular member arranged between the clutch cover 521 and the pressureplate 22. The diaphragm spring 523 has a radially middle portion whichis supported by the clutch cover 521 through the two wire rings 27. Thewire rings 27 are held by a plurality of tags 98 which extend from theinner peripheral edge of the bottom of the clutch cover 521 and havebent or curved forms. The outer peripheral end of the diaphragm spring523 is in contact with the pressure plate 22 and biases the pressureplate 22 toward the flywheel 2. The diaphragm spring 523 is providedwith slits 96 extending radially inward from the portion near the outerperipheral end, as can be seen in FIG. 18. These slits 96 define aplurality of levers 95. The diaphragm spring 523 is provided at itsradially middle portion with a plurality of circumferentially equallyspaced apertures 97. Each aperture is circumferentially concentric withthe corresponding slit 96. The aperture 97 has a diameter which allowsinsert of a box tool 550 for fastening the bolt 11A. As shown in FIG.19, the diaphragm spring 523 is provided at portions around theapertures 97 with burrings 501 which project substantiallyperpendicularly to the plane of the diaphragm spring 523 and have apredetermined height. Therefore, the diaphragm spring 523 can have ahigh lever rigidity in spite of provision of the apertures 97.

The clutch disk assembly 4 is basically formed of the clutch engagementportion 31 similar to that already described in the first embodiment aswell as the hub 34 and the plate 17. The inner peripheral portion of theplate 17 is fixed to the flange of the hub 34 by the rivets 19. Theouter peripheral portion of the plate 17 is fixed to the clutchengagement portion 31 by the rivets 18. A plurality of apertures 20 areformed at a radially middle portion of the plate 17. Each aperture 20has a diameter allowing insert of the box tool 550 for fastening thebolt 11A. The hub 34 has a spline aperture coupled to the main driveshaft 6 of the transmission.

In the assembly process of the modular clutch 1, apertures for the pin93 are aligned with each other prior to fixing of the clutch cover 521to the flywheel 2. Thereby, the aperture 2i of the flywheel 2 is axiallyaligned with the aperture 93 of the diaphragm spring 523.

The assembled modular clutch 500 is fixed to the crank shaft 5 by thefollowing manner. The aperture 20 of the plate 17 of the clutch diskassembly 4 is aligned with the apertures 97 and 2i. Thereby, theapertures 2i, 20 and 97 formed at the parts of the modular clutch 1 areaxially aligned together. Then, the modular clutch 1 is fitted aroundthe crank shaft 5. At this operation, the radially inward flange of theflywheel 2 is brought into close contact with the end surface of thecrank shaft 5, and the thread apertures 5a of the crank shaft 5 arealigned with the apertures 2i of the flywheel 2. In this state, the boxtool 550 holding the bolt 11a is inserted from the transmission sideinto the apertures 97, 20 and 2i of the diaphragm spring 23, plate 17and flywheel 2, and the bolt 11a is inserted into the thread aperture 5aof the crank shaft 5 for fastening the same.

In a modification of this embodiment, as shown in FIG. 20, the diaphragmspring 523 may be provided around the apertures 97 with drawn portions502 for ensuring a sufficient rigidity. Since the rigidity of the leversof the diaphragm spring is not reduced as described above, the clutchcan maintain a sufficiently sharp disengaging property.

Eight Embodiment

A modular clutch 601 shown in FIGS. 21 to 23 is basically formed of aflywheel 102, a clutch cover assembly 103, a clutch disk assembly 104and a damper mechanism 109. An engine (not shown) is arranged at theleft side in FIGS. 22 and 23, and a transmission (not shown) is arrangedat the right side. The modular clutch 601 is operable to transmit andinterrupt the torque from a crank shaft 105 of the engine to a maindrive shaft 106 extending from the transmission. In FIGS. 22 and 23,O--O represents a rotation axis of the modular clutch 601.

A flexible plate 107 and an inertia member 117 (second flywheel) isarranged at the end of the crank shaft 105. The flexible plate 107 is acircular plate member, and a circular plate member 114 is fixed to theinner peripheral portion thereof by rivets 115. The inner peripheralportion of the flexible plate 107 is fixed to the crank shaft 105 at theengine side together with the plate member 104 by bolts 112. Theflexible plate 107 is provided at its radially middle portion with aplurality of circumferentially equally spaced round apertures 107a. Theflexible plate 107 has a high rigidity in the circumferential direction,but is flexible in the bending direction.

The inertia member 117 is fixed to the outer peripheral end of theflexible plate 107 by the rivets 116. The inertia member 117 is anaxially extended cylindrical member. A ring gear 113 is fixed to theinertia member 117. The inertia member 117 is provided atcircumferentially equally spaced three positions with manipulationapertures 117a for communicating the radially inner and outer sides witheach other.

As described above, the flexible plate 107 and inertia member 117 arearranged in advance at the crank shaft side, and the modular clutch 601is attached thereto, as described below.

The damper mechanism 109 is basically formed of a first input plate 141,a second input plate 142, a bent plate spring 146 and a driven member143. The first input plate 141 is circular and is arranged beside theflexible plate 107. The first input plate 141 has an outer peripheralportion which is in contact with an inner peripheral surface of theinertia member 117. The first input plate 141 has a radially middleportion which is convexed toward the transmission. The second inputplate 142 is circular and is arranged beside the first input plate 141.The second input plate 142 has an outer peripheral end which is incontact with the inner peripheral surface of the inertia member 117. Theouter peripheral portions of the first and second input plates 141 and142 are in contact with each other, and are fixed together by rivets 148with a seal ring 150 therebetween. The inner peripheral portion of thefirst input plate 141 extends radially inward beyond the inner peripheryof the second input plate 142. The inner peripheral portion of the firstinput plate 141 is formed with an inner projection 141b having acylindrical shape extending away from the engine side.

The outer peripheral portions of the first and second input plates 141and 142 are fixed to the inertia member 117 by three circumferentiallyequally spaced bolts 111B. The bolts 111B are attached from thetransmission side. The inertia member 117 is provided with grooves 117bat positions corresponding to the bolts 111B, respectively.

An annular space defined between the first and second input plates 141and 142 forms a spring accommodating chamber. A pair of bent platesprings 146 are disposed within the spring accommodating chamber.

The bent plate spring 146 arranged in each arc-shaped chamber isdescribed below. As shown in FIG. 21, each bent plate spring 146 is madeof an elongated plate having a predetermined width, the elongated platebeing bent into an undulated, or corrugated form defining a plurality ofspring portions laid side by side in series, each spring portion havingone each of ring portions 211 and 212 and lever portions 213, allcontinuously formed. The outer ring portions 211 and inner ring portions212 are arranged alternately to each other, and have ends, which formcircumferentially small spaces opposed to each other. Each end isconnected to the end of the opposed ring portion by the lever portion213. The ring portions 213 diverge from the ring portion 211 or 212toward the ring portions 212 or 211. Each of the ring portions 211 and212 has such an irregular section such that its thickness graduallydecreases from the end toward the center, and therefore has a lowerrigidity than the lever portion 213. The outer ring portion 211 has alarger diameter than the inner ring portion 212. Use of the bent platespring 146 makes it possible to minimize the axial dimensions of theviscosity damper mechanism 109 when compared to a similar device havingcoil springs.

The spring accommodating chamber is filled with powder solid lubricantsuch as molybdenum disulfide. The powder solid lubricant is mixed withair and is disposed in the spring accommodating chamber. Also, thepowder solid lubricant easily adheres onto surfaces of the walls of thespring accommodating chamber, i.e., surfaces of the first input plate141, second input plate 142, driven member 143 and bent plate spring146. The powder solid lubricant lubricates the respective slidingportions. As a result, the damper mechanism 109 can have an increasedlifetime.

The powder solid lubricant filling the damper mechanism 109 requires thefollowing characteristics.

(1) It has a low friction coefficient and provides a good lubricity.

(2) It provide a good adhesive property with respect to each member(metal member).

(3) It can be strongly stuck onto each member after adhering thereto.

Since the powder solid lubricant generally remains on the surfaces ofall of the sliding portions, the lubricity can be maintained for a longterm.

(4) It is light and is likely to disperse.

(5) It does not have self-condensing properties.

(6) It has a good heat resistance.

(7) It is not an injurious material.

FIG. 24 shows the characteristics of a variety of solid lubricants, allof which may be used in the present invention. However, based oncharacteristics in FIG. 24, it can be understood that the molybdenumdisulfide can be employed most preferably as the solid lubricant in viewof good absorptive properties and large adhesive force. Further, themolybdenum disulfide can be used under a high load, and is inexpensive.Tungsten disulfide is second most preferable substance.

The spring accommodating chamber may be filled with fluid such as greaseor working fluid. In this case, a viscosity resistance is generated byexpansion and shrinkage of a plurality of fluid-filled spaces defined bythe bent plate springs 146 in the spring accommodating chamber.

The driven member 143 is a circular member, and integrally has engagingportions 143a which extend radially outward. The engaging portions 143aextend through the spring accommodating chamber, and each are in contactwith circumferentially adjacent ends of the paired bent plate springs146. The first and second input plates 141 and 142 have support portions141a and 142a which project axially and are in contact with thecircumferentially opposite ends of the bent plate springs 146.

The flywheel 102 has the flat friction surface 102a at the transmissionside of its outer peripheral portion. The flywheel 102 is also providedwith communication apertures 102j which are located radially inside thefriction surface 102a and extend between the opposite sides. The drivenmember 143 is fixed to the radially inner end of the flywheel 102 by therivets 160. The inner peripheral portions of the flywheel 102 and thedriven member 143 are carried by an inner projection 141b of the firstinput plate 141 through a bearing 661. The flywheel 102 is provided atits outer peripheral surface with circumferentially equally spaced threeengaging portions 102k (FIG. 22), which project radially outward. An endof each engaging portion 102k near the engine is inclined to increase adepth as the position moves radially inward.

The clutch cover assembly 103 is basically formed of a clutch cover 621,a pressure plate 122, a diaphragm spring 123, a coupling plate 128, studpins 126, two wire rings 127 and a conical spring 129.

The clutch cover 621 is a dish-like plate member provided at its centerwith a large aperture, and is provided at its outer peripheral portionwith circumferentially equally spaced three extensions 162 having apredetermined width and extending toward the flywheel 102. Eachextension 162 is provided at its end with a bend portion 163 which isbent radially inward. Each bent portion 163 is engaged with the engagingportion 102k of the flywheel 102. Thereby, the clutch cover 621 isunmovable toward the transmission with respect to the flywheel 102. Theextension 162 is provided at its end with a circumferentially extendingrecess with which a circumferentially extending plate 164 is engaged.The plate 164 is fixed to the outer peripheral surface 102b of theflywheel 102 by bolts 165. Owing to the above structure, the clutchcover 621 is unrotatable with respect to the flywheel 102.

The pressure plate 122 is an annular member arranged inside the clutchcover 621. The pressure plate 122 is provided with a pressing surface122a opposed to the friction surface 102a of the flywheel 102. In thepressure plate 122, there is formed an annular projection 122bprojecting toward the transmission and located at the surface oppositeto the pressing surface 122a. The pressure plate 122 has a radiallyinward flange 122c.

The diaphragm spring 123 is a circular member, and is disposed betweenthe clutch cover 621 and the pressure plate 122. The diaphragm spring123 has an annular elastic portion 123a and a plurality of levers 123bextending radially inward from the portion 123a. There are formed firstapertures 123c located between but radially outside the plurality oflevers 123b. Correspondingly to the slits, there are formedcircumferentially equally spaced three second apertures 123d. The secondaperture 123d extends radially inward beyond the first aperture 123c toa position near the flange 122c of the pressure plate 122. The annularelastic portion 123a has a radially inner end, of which opposite sidesare carried by the wire rings 127, and also has a radially outer endwhich in contact with the annular projection 122b of the pressure plate122. In this state, the elastic portion 123a biases the pressure plate621 toward the flywheel 102.

A supporting structure 125 for supporting the diaphragm spring 123 willbe described below. The plurality of stud pins 126 fixed to the radiallyinner end of the bottom of the clutch cover 621 extend through the firstapertures 123c of the diaphragm spring 123 toward the pressure plate122. The other end of each stud pin 126 is fixed to the coupling plate128 which is described below. Radially outside the stud pins 126, thewire rings 127 are arranged between the coupling plate 128 (describedbelow) and the diaphragm spring 123 and between the diaphragm spring 123and the bottom of the clutch cover 621, respectively. Thus, the radiallyinner portion of the elastic portion 123a of the diaphragm spring 123 ispinched between the paired wire rings 127.

The coupling plate 128 is annular, and is integrally provided at itsinner periphery with three coupling portions 128a, each of which has along arc-shaped form and circumferentially extends in a directionindicated by R1 in FIG. 21. The end of this coupling portion 128a isfixed to the flange 122c of the pressure plate 122 by a rivet 122c. Therivet 122c is located at a position corresponding to the second aperture123d of the diaphragm spring 123. The coupling portion 128a has a highrigidity in the circumferential direction but is flexible in the axialdirection. The coupling portion 128a biases the pressure plate 122 awayfrom the flywheel 102.

The conical spring 129 is arranged at the radially outer portion of thecoupling plate 128. The radially inner end of the conical spring 129 issupported by the coupling plate 128. The radially outer end thereofbiases the radially outer end of the diaphragm spring 123, i.e., aportion adjacent to the annular projection 122b of the pressure plate122 away from the pressure plate 122.

As described above, the coupling plate 128 couples the clutch cover 621and the pressure plate 122 together, and supports the conical spring129. Since the coupling plate 128 has multiple functions as describedabove, the parts can be reduced in number.

The plurality of engaging portions 164 are fixed to the pressure plate122 by fixing pins 165, and have ends which hold together with theannular projection 122b of the pressure plate 122 the radially outer endof the diaphragm spring 123 located between them. The extension 162 isprovided at the position corresponding to each engaging portion 164 withthe aperture 621c, as shown in FIG. 22.

The clutch disk assembly 104 is basically formed of the clutchengagement portion 131 similar to that described above with respect toother embodiments, a hub 134 and a plate 166. The clutch engagementportion 131 is disposed between the friction surface 102a of theflywheel 102 and the pressing surface 122a of the pressure plate 122.The hub 134 is spline-engaged with the main drive shaft 106. The plate166 has an inner peripheral portion fixed to the flange of the hub 134by rivets 119, and an outer peripheral portion fixed to the clutchcoupling portion 131 by rivets 118 (see FIG. 23). The plate 166 isprovided with a plurality of circumferentially equally spaced apertures166a.

The main drive shaft 106 extending from the transmission has an endcarried by the crank shaft 105 through a bearing 169. The release device108 is axially movably arranged around the main drive shaft 106. Therelease device 108 has an end engaged with the side surfaces, which areopposed to the transmission, of the ends of the levers 123b of thediaphragm spring 123. When the release device 108 moves toward theengine to move the levers 123b toward the engine, the biasing force ofthe elastic portion 123a against the pressure plate 122 is released.

Although FIG. 22 shows bolts 200, the bolts 200 are not used for actualoperation of the modular clutch 601. The bolts 200 are used forattaching and detaching the clutch cover assembly 103 to and from theflywheel 102. The plurality of bolts 200 extend through the aperturesformed at the radially inner portion of the bottom of the clutch cover621, the first apertures 123c of the diaphragm spring 123 and thecoupling plate 128, and are screwed into the pressure plate 122, as isdescribed below.

Now, operation of the modular clutch 601 is described.

When the crank shaft 105 of the engine rotates, a torque is transmittedthrough the flexible plate 107 to the modular clutch 601. The torque istransmitted through the damper mechanism 109 to the flywheel 102, and isoutput to the clutch disk assembly 104. The pressure plate 122 rotatestogether with the clutch cover 621 coupled thereto by the coupling plate128. In this manner, the rotary driving of the pressure plate 122 isperformed by the coupling plate 128 coupling the radially inner portionsof the pressure plate 122 and the clutch cover 621 together, so that itis not necessary to provide a recess for accommodating a strap plate atthe outer peripheral portion of the clutch cover 621, which is requiredin the prior art.

Since the inertia member 117 is fixed to the first and second inputplates 141 and 142, a sufficiently large inertia can be ensured at theinput and output systems of a power which is separated from each otherby the bent plate springs 146. As a result, the resonant frequency canbe lower than the service rotation speed of the engine. Since theinertia member 117 is arranged at the radially outer position, the firstand second input plates 141 and 142 which are members defining thespring accommodating chamber can have reduced axial sizes. Consequently,the modular clutch 601 can have a reduced axial size as a whole. Sincethe inertia member 117 is axially long, the whole structure does nothave an increased radial size. As described above, the arrangement ofthe inertia member 117 at the radially outer position of the dampermechanism 109 does not increase the radial size of the whole apparatusowing to the fact that the clutch attachment seat is eliminated from theflywheel 102 and therefore the inertia member 117 can be arranged at amore radially inner position.

When a bending vibration is transmitted from the crank shaft 105, theflexible plate 107 bends in the bending direction to absorb thevibration.

When the torsional vibration is transmitted from the engine, the dampermechanism 109 allows periodical relative rotation of the first andsecond input plates 141 and 142 with respect to the driven member 143.In this operation, the bent plate spring 146 is compressed in thecircumferential direction, and thereby effectively dampens the torsionalvibration.

When a driver depresses a clutch pedal, an end of the release device 108moves the levers 123b of the diaphragm spring 123 toward the engine. Asa result, the radially outer end of the elastic portion 123a is spacedfrom the annular projection 122b of the pressure plate 122. Thereby, thebiasing force by the coupling portion 128a of the coupling plate 128moves the pressure plate 122 away from the clutch coupling portion 131of the clutch disk assembly 104. As a result, the torque from theflywheel 102 to the clutch disk assembly 104 is interrupted. In theabove releasing operation, the conical spring 129 applies a loaddirected toward the transmission to the diaphragm spring 123, so thatthe release load lowers and provides a flat characteristic curve,resulting in reduction in force required for depressing the clutchpedal.

Now, assembly and attachment of the modular clutch 601 is described.

The flywheel 102 and the damper mechanism 109 are fixed together inadvance by the rivets 160. In the clutch cover assembly 103, the clutchcover 621 and the pressure plate 122 are axially unmovably fixedtogether by the bolts 200. The bolts 200 maintain the clutch cover 621and the pressure plate 122 at adjacent positions in spite of applicationof the load by the diaphragm spring 123. The clutch cover assembly 103thus assembled is moved toward the flywheel 102, and the extension 162of the clutch cover 621 is moved through the space between the engagingportions 102k of the flywheel 102. In this state, the clutch cover 621is rotated to engage the bent portion 163 with the engaging portion102k. Then, the bolt 165 and the plate 164 are manipulated through themanipulation aperture 117a for fixing the structure to the flywheel 102,so that the clutch cover 621 is unrotatably fixed to the flywheel 102.The bolts 200 are removed, so that the diaphragm spring 123 biases thepressure plate 122 and the clutch cover 621 axially away from eachother. As a result, the bent portion 163 is strongly biased toward thetransmission with respect to the engaging portion 102k.

The modular clutch 102 thus completed is fixed by the plurality of bolts111B to the flexible plate 107 and the inertia member 117 which arealready fixed to the crank shaft 105. The bolt 111B extends through aportion of the clutch cover 621 not provided with the extension 162, theportion of the flywheel 102 not provided with the engaging portion 102kand the groove 117b of the inertia member 117, and fixes the outerperipheral portions of the first and second input plates 141 and 142 tothe inertia member 117. Owing to the fact that the bolt 111b is fixedfrom the transmission side in this manner, the workability is improvedcompared with the prior art.

According to the modular clutch 601, the clutch disk assembly 104 usesthe friction facings made of metallic sintered members as alreadydescribed in the embodiments, it can be used for a longer term.Therefore, it may not be necessary to replace the clutch disk assembly104. In this case, the lifetime extends until expiration of the lifetimeof the flywheel 102 itself. It should be appreciated that the bolt 165and plate 164 in the present embodiment could be replaced with rivets orwelds, as is described above with respect to other embodiments.

Since the clutch disk assembly 104 is provided at the plate 166 with theaperture 166a, and the flywheel 102 is provided with the communicationaperture 102j, air flows through these apertures and thereby cools theclutch engagement portion 131. Since the clutch cover 621 is providedwith the aperture 621c, and the clutch engagement portion 131 is openedradially outward through portions not provided with the extensions 162.Further, a heat of the clutch engagement portion 131 can be escapedthrough the manipulation aperture 117a. Owing to these apertures, theclutch engagement portion 131 can be sufficiently cooled. As a result,it is possible to suppress disadvantages such as deformation of theplate 166 due to a heat generated from the clutch engagement portion131.

For exchanging the clutch disk assembly 104, the clutch cover 621 andthe pressure plate 122 are fixed together by the bolts 200 again. Then,the bolts 165 and the plate 164 are removed, and the clutch coverassembly 103 is rotated to disengage the bent portion 163 from theengaging portion 102k. As described above, exchange of the clutch diskassembly 104 simply requires remove of the clutch cover assembly 103from the flywheel 102, and therefore requires only a simple operation.

Ninth Embodiment

A modular clutch 701 shown in FIG. 25 has a structure similar to thoseof the foregoing embodiments. In this modular clutch 701, the inertiamember 117 forms a member of the modular clutch 701. More specifically,the outer peripheral portions of the first and second input plates 141and 142 are welded to the inertia member 117. The modular clutch 701thus constructed is attached to the flexible plate 107 which is alreadyfixed to the crankshaft 105. More specifically, the radially outerportion of the flexible plate 107 is fixed to the radially inner portionof the inertia member 117 by bolts 111C. The bolts 111C are manipulatedfrom the engine side, and are screwed into the inertia member 117.

According to the modular clutch of the invention, since the clutch diskassembly has the friction facing made of the metallic sintered member,the friction facing can have a significantly increased lifetime, so thatthere is a large possibility that the modular clutch can be used untilexpiration of the lifetime of the flywheel. As a result, exchange of theclutch disk assembly may not be required, so that no problem arises evenif the clutch cover and the flywheel are unremovably fixed together by asimple structure.

Various details of the present invention may be changed withoutdeparting from its spirit or its scope. Furthermore, the foregoingdescription of the embodiments according to the present invention areprovided for illustration only, and not for the purpose of limiting theinvention as defined by the appended claims and their equivalents.

What is claimed is:
 1. A modular clutch construction comprising:aflywheel having an outer radial surface and an axial face; an annularpressure plate having an outer radial face, said annular pressure platebeing coaxially disposed adjacent to said flywheel and facing said axialface of said flywheel; a clutch cover encompassing said outer radialsurfaces of said pressure plate and said flywheel, a radial innersurface of said clutch cover contacting said outer radial surface ofsaid flywheel at a contact position; a ring gear fitted onto aperipheral surface of said clutch cover radially over said contactposition, said ring gear being shrunk fitted on said peripheral surfaceof said clutch cover; a plurality of axially extending slits formedcircumferentially spaced on an interior margin of said clutch cover atsaid contact position; a clutch disc assembly coaxially disposed betweensaid pressure plate and said flywheel, friction portions of said clutchdisk assembly being formed of a sintered metal material; and whereinsaid flywheel and said annular pressure plate are made of cast ironcontaining Cr, V and a rare earth element added thereto.
 2. The modularclutch construction according to claim 1, wherein a positioning meansmaintains a fixed relative position between said clutch cover and saidflywheel.
 3. The modular clutch construction according to claim 2,wherein said positioning means includes a plurality of holes formed insaid clutch cover and said flywheel having pins inserted therein, saidholes being spaced respectively about the circumference of said clutchcover and said flywheel in alignment with said contact position.
 4. Themodular clutch construction according to claim 2, wherein saidpositioning means includes an abutment portion formed as a radiallyinward step on said clutch cover, said abutment portion abutting saidaxial face of said flywheel at a radially outward position.
 5. Themodular clutch construction according to claim 4, further comprising aflexible plate mountable to a second axial face of said flywheel.
 6. Amodular clutch construction comprising:a flywheel having an outer radialsurface and an axial face; an annular pressure plate having an outerradial face, said annular pressure plate being coaxially disposedadjacent to said flywheel and facing said axial face of said flywheel; aclutch cover encompassing said outer radial surfaces of said pressureplate and said flywheel, a radial inner surface of said clutch covercontacting said outer radial surface of said flywheel at a contactposition; a ring gear fitted onto a peripheral surface of said clutchcover radially over said contact position, said ring gear being shrunkfitted on said peripheral surface of said clutch cover; a plurality ofaxially extending slits formed circumferentially spaced on an interiormargin of said clutch cover at said contact position; and a clutch discassembly coaxially disposed between said pressure plate and saidflywheel, wherein said clutch disk assembly further includes:a coreplate fixed to a radially outer portion of said clutch disk assembly, aplurality of friction facings being retained proximate said core platesuch that said friction facings may undergo limited movement in an axialdirection with respect to said core plate; a cushioning member retainedbetween said friction facings and said core plate, said cushioningmember being deformable in response to movement in the axial directionof said friction facings; and said friction facing of said clutch diskassembly are formed of a sintered metal material.
 7. The modular clutchconstruction according to claim 6, wherein a positioning means maintainsa fixed relative position between said clutch cover and said flywheel.8. The modular clutch construction according to claim 7, wherein saidpositioning means includes a plurality of holes formed in said clutchcover and said flywheel having pins inserted therein, said holes beingspaced respectively about the circumference of said clutch cover andsaid flywheel in alignment with said contact position.
 9. The modularclutch construction according to claim 7, wherein said positioning meansincludes an abutment portion formed as a radially inward step on saidclutch cover, said abutment portion abutting said axial face of saidflywheel at a radially outward position.
 10. The modular clutchconstruction according to claim 9, further comprising a flexible platemountable to a second axial face of said flywheel.
 11. The modularclutch construction according to claim 6, wherein said flywheel and saidannular pressure plate are made of cast iron containing Cr, V and a rareearth clement added thereto.